[router] allow router launch server to use grpc mode (#11600)

sgl-router/py_src/sglang_router/launch_server.py

 import argparse
+import asyncio
 import copy
 import logging
 import multiprocessing as mp
@@ -13,7 +14,6 @@ import requests
 from setproctitle import setproctitle
 from sglang_router.launch_router import RouterArgs, launch_router
 
-from sglang.srt.entrypoints.http_server import launch_server
 from sglang.srt.server_args import ServerArgs
 from sglang.srt.utils import is_port_available
 
@@ -72,6 +72,14 @@ def run_server(server_args, dp_rank):
     # Set SGLANG_DP_RANK environment variable
     os.environ["SGLANG_DP_RANK"] = str(dp_rank)
 
+    # Launch server in appropriate mode (HTTP or gRPC)
+    if server_args.grpc_mode:
+        from sglang.srt.entrypoints.grpc_server import serve_grpc
+
+        asyncio.run(serve_grpc(server_args))
+    else:
+        from sglang.srt.entrypoints.http_server import launch_server
+
         launch_server(server_args)
 
 
@@ -186,8 +194,10 @@ def main():
     )
 
     # Update router args with worker URLs
+    # Use grpc:// protocol if server is in gRPC mode, otherwise http://
+    protocol = "grpc" if server_args.grpc_mode else "http"
     router_args.worker_urls = [
-        f"http://{server_args.host}:{port}" for port in worker_ports
+        f"{protocol}://{server_args.host}:{port}" for port in worker_ports
     ]
 
     # Start the router